The Nutcracker and the Four Realms: The Secret of the Realms by Meredith Rusu (HC)

When Clara Stahlbaum receives a beautiful yet mysterious egg-shaped box from her late mother, she wonders what it means  Searching for answers Clara soon finds herself in a magical world - the Four Realms.

Years earlier, Clara's mother, Marie, is a lonely orphan adopted by an eccentric inventore.  She stumbles upon an unbelievable place and decides to apply her mechanical skills in magical ways.